Tropical Storm ONE Advisory Tue Jul 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (HALOLA)
WARNING NR 44//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TROPICAL STORM 01C (HALOLA), LOCATED APPROXIMATELY 211 NM
SOUTHEAST OF IWO TO, HAS TRACKED WEST-NORTHWESTWARD AT 14 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MUTISPECTRAL SATELLITE IMAGERY
DEPICTS TIGHTLY CURVED BANDING WRAPPING AROUND THE NORTHERN AND
WESTERN CORE OF THE CYCLONE INTO A WELL-CONSOLIDATED LOW LEVEL
CIRCULATION CENTER (LLCC). THE CIMSS TOTAL PRECIPITABLE WATER
ANIMATION SHOWS A RADIALLY EXPANDING MOISTURE FIELD WITH AN
ESTABLISHED EQUATORWARD OUTFLOW CHANNEL. A 202142Z SSMIS MICROWAVE
IMAGE DEPICTS A DEVELOPING BANDING EYE FEATURE. THE INITIAL POSITION
IS BASED ON THE AFOREMENTIONED IMAGERY WITH HIGH CONFIDENCE. THE
CURRENT INTENSITY HAS BEEN INCREASED TO 60 KNOTS BASED ON AN AVERAGE
OF THE DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND RJTD. THE
RECENT INTENSIFICATION HAS BEEN ACCELERATED BY LOW VERTICAL WIND
SHEAR (VWS), EXCELLENT DIFFLUENCE ALOFT, AND WARM SEA SURFACE
TEMPERATURES (SSTS). TS 01C IS TRACKING ALONG THE SOUTHERN PERIPHERY
OF THE DEEP-LAYERED STR.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS HALOLA WILL CONTINUE TRACKING ON A WEST-NORTHWESTWARD
TRAJECTORY UNDER THE STEERING INFLUENCE OF THE DOMINANT STR THROUGH
TAU 72. THE SYSTEM IS FORECAST TO INTENSIFY OVER THE NEXT 36 HOURS
DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS WITH GOOD OUTFLOW, LOW
VWS, AND SSTS ABOVE 28 CELSIUS. BEYOND TAU 24, VWS WILL REACH 20 TO
25 KNOTS WHICH WILL CAUSE THE RATE OF INTENSIFICATION TO DECREASE.
DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72, LENDING
TO HIGH CONFIDENCE IN THIS PORTION OF THE FORECAST.
   C. IN THE EXTENDED TAUS, THE SYSTEM WILL BEGIN TO TURN POLEWARD
AS IT ROUNDS THE SOUTHWESTERN PERIPHERY OF THE STEERING STR. TS
HALOLA SHOULD BEGIN TO WEAKEN DUE TO VWS ABOVE 30 KNOTS,
DUE TO STRONG NORTHERLY FLOW FROM A BUILDING MID-LATITUDE RIDGE TO
THE NORTHWEST, AND SSTS DROPPING BELOW 26 CELSIUS. DYNAMIC MODEL
GUIDANCE SPREADS OUT AFTER TAU 72 DUE TO VARYING DEGREES IN THE
TIMING OF THE RE-CURVE. THIS FORECAST HAS AGAIN SHIFTED SLIGHTLY
FURTHER WESTWARD FROM THE PREVIOUS FORECAST DUE TO VARYING MODEL
SOLUTIONS IN THE EXTENT OF THE STR TO THE NORTH. THIS UNCERTAINTY
LEADS TO AN OVERALL LOW CONFIDENCE IN THE JTWC FORECAST. AT THIS
TIME, TS HALOLA IS NOT EXPECTED TO UNDERGO EXTRA-TROPICAL TRANSITION
SOUTH OF JAPAN DUE TO THE POSITIONING OF THE BAROCLINIC ZONE NEAR 40
DEGREES LATITUDE.//
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